I'd love to be able to define a specific group of classes, for instance, everything affiliated with navigation, and put them in a collapsible group. Sub-groups inside a group would be awesome too. This would make a large css sheet so much more manageable. I've tried LESS and other techniques but I feel like it's a problem that could be solved with proper structure and collapse within sublimetext. Example below. If this exists, please, for the love of god, someone tell me how. Thanks!

<!-- Group starts here that would be collapsible -->.first_class {}.second_class {} <!-- This would be a sub collapsible group under second_class --> .second_class p { } .second_class h1 { }<!-- Another group starts here that would also be collapsible -->

Almost all in CSS syntax including folding options is defined in Packages/CSS/CSS.tmLanguage file. It's a XML file which you can edit to add you own features. I'm not sure but probably it's a good idea to copy it to User package to prevent loosing on upgrades. I haven't loosed anything, but probably just because the file wasn't changed in newer versions of editor.